Far be it from this African American youngster and his mother to saunter down the street just any old way. They first ``zig-zag walk''and then take ``big giant steps and talk in loud giant voices''; sometimes they glide along in ``slow-motion steps,'' discussing ``molasses and birthdays and how long they take.'' This playful ritual shows a tender, affectionate mother-son relationship, made all the more fun by the parent's willingness to join in this original perambulation. Hays's ( Abiyoyo ) soft pastels capture the sights and feeling of urban life as the two pass stores, a park's fountain and graffiti-covered walls, pausing to dance by a building stoop. Smalls-Hector's ( Irene and the Big, Fine Nickel ) lively, melodious language gives a joyful sense of this shared experience; particularly inventive is the manner in which the protagonists' conversational gambits match their gait of the moment. Mothers and offspring alike will delight in the final picture, as down the street these characters meander, appropriately taking ``Jonathan-and-Mommy steps'' toward home. Ages 4-8. (Oct.)